This invention relates to smoke alarms and particularly to attachments for rendering conventional battery operated smoke alarms more useful.
It has long been recognized that detection of smoke in dwellings, stores, restaurants and other buildings defining spaces to be occupied is a major way in which loss of life by fire can be reduced, and use of the so-called single station smoke alarm has become a standard practice. While the many types of such alarms now available differ widely as to detail, they ordinarily comprise a housing which carries an electrically operated signal device, usually a sounder, a smoke responsive device operative to provide a control signal to the signal device when subjected to smoke, a battery for operating the signal device, and circuit means interconnecting the signal device, smoke responsive device and battery. Such alarms are usually mounted on a ceiling or in an elevated location on a wall and ordinarily can be reached, as for replacing the battery, only by climbing a short ladder or the like.
While such smoke alarms have received wide acceptance, their installation now being required by law in many areas, they present two problems. First, in order to be adequately sensitive to provide early detection of smoke in the event of a threatening fire, the alarms respond to smoke produced intentionally and not representing the threat of fire. For example, when such an alarm is installed on the ceiling of a hallway adjacent a kitchen, the alarm frequently responds to smoke resulting from broiling food in the kitchen. Similarly, installed on the ceiling of an eating space in a restaurant, when the eating space is near the doorway to the restaurant kitchen, such an alarm responds to smoke from the kitchen, admitted to the eating space each time the door is opened when carrying food to the eating space. So as to be readily noticed, the audible sound of the alarm is persistent and irritating and, when the purposely produced smoke condition is such as to continue for a period of time, the only relief is to climb up and deactivate the smoke alarm, usually by disconnecting the battery. The second problem stems from the fact that, with time, the battery or batteries become discharged so that the smoke alarm becomes inoperative. While the battery or batteries can be replaced readily, this requires climbing to within reach of the smoke alarm and there is a strong human tendency to delay replacing the battery. Many such alarms are designed to alert the user of impending battery failure by emitting periodic short sounds, but although such warnings occur over a relatively long period of time they are frequently ignored. In some cases, the two problems aid each other, since the user who has recently been irritated by having to deactivate the alarm because it responded to purposely produced smoke is more likely to delay replacing the battery when it has become discharged, and the user who has to deactivate the alarm because it is responding to purposely produced smoke is likely to leave the battery disconnected for awhile.
Though the tendency for such smoke alarms to respond to purposely produced smoke, and thus be irritating, clearly works against the purpose of the alarm, proposals for providing easy ways to temporarily deactivate the alarm have apparently had little acceptance. Though the design of the alarm can be changed to provide a deactivating switch, as disclosed in U.S. Pat. No. 4,313,110 to Subulak et al, that could best be done by the manufacturer of the smoke alarm, and the alarm manufacturers appear not to have accepted the need for change. There has accordingly been a continuing need for improvement.